Stability and accuracy of 3D neutron transport simulations using the 2D/1D method in MPACT
by Benjamin S. Collins, Shane G. Stimpson, Blake W. Kelley, Mitchell T.H. Young, Brendan M. Kochunas, Aaron M. Graham, Edward W. Larsen, Thomas J. Downar, Andrew T. Godfrey
A consistent “2D/1D” neutron transport method is derived from the 3D Boltzmann transport equation, to calculate fuel-pin-resolved neutron fluxes for realistic full-core Pressurized Water Reactor (PWR) problems. The 2D/1D method employs the Method of Characteristics to discretize the radial variables and a lower order transport solution to discretize the axial variable. This paper describes the theory of the 2D/1D method and its implementation in the MPACT code, which has become the whole-core deterministic neutron transport solver for the Consortium for Advanced Simulations of Light Water Reactors (CASL) core simulator VERA-CS. Several applications have been performed on both leadership-class and industry-class computing clusters. Results are presented for whole-core solutions of the Watts Bar Nuclear Power Station Unit 1 and compared to both continuous-energy Monte Carlo results and plant data.